[RT PATCH] kernel/irq: make irq_set_affinity_notifier() work on old_notify consistently

[Juri Lelli]

The second half of irq_set_affinity_notifier() flushes an old notifier,
but (for RT) it is currently working on 'notify', which is the new one
(or can be NULL - in fact a NULL pointer dereference has been observed).

Fix this by making the second half of irq_set_affinity_notifier() use
old_notify consistently.

Fixes: d4200ab75cdd ("genirq: Handle missing work_struct in 
irq_set_affinity_notifier()")
Signed-off-by: Juri Lelli <juri.le...@redhat.com>
---
Hi,

This applies to v4.19.59-rt24 (and to all the other branches that have
the patch that introduced the issue). v5.2-rtx doesn't have this problem
(thanks to the workqueue rework).

Best,

Juri
---
 kernel/irq/manage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index b2736d7d863b..4586967a1b32 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -386,7 +386,7 @@ irq_set_affinity_notifier(unsigned int irq, struct 
irq_affinity_notify *notify)
 
        if (old_notify) {
 #ifdef CONFIG_PREEMPT_RT_BASE
-               kthread_cancel_work_sync(&notify->work);
+               kthread_cancel_work_sync(&old_notify->work);
 #else
                cancel_work_sync(&old_notify->work);
 #endif
-- 
2.17.2